In the field of information processing devices like servers, there is a growing need for rapid access to large quantities of data, such as databases (DB), in the coming era of “big data”. The trend toward enlarging main storage (DRAM) has yet to catch up with that need, in part because of the lagging 3D memory packaging technology (TSV). Besides, DRAMs have a difference in throughput (latency) on the order of 106 to SAS (Serial Attached SCSI)-connected SSDs (Solid State Drive) or HDDs (Hard Disk Drive), which are auxiliary storage devices.
Now that PCI-connected SSDs (PCI-SSD) have been commercialized for offering response rates that fall response rates between the response rates of DRAM and the SAS-connected SSD (SAS-SSD), the market for this product is expected to grow in the future.
Patent Literature 1 discloses an FBDIMM (Fully Buffered DIMM) in which flash memories and DRAMs are mounted on different DIMMs (Dual Inline Memory Module) and connected in a daisy-chain manner of a serial transmission system via serial transmission buffer elements mounted on each module. A Memory controller is provided to transmit serialized control signals, address signals, and write data signals to the DIMMs and receive serialized read data signal from the DIMMs in accordance with the FBDIMM signal transmission protocol.